Facilitatory and Inhibitory Mesencephalic Influence on Gonadotropin Release

Abstract

It is well known that the maintenance of a basic level of gonadotropin secretion by the anterior pituitary depends on its connection with the hypothalamus. This neural structure contains neurons which elaborate chemical agents that regulate pituitary hormone secretion after reaching the gland by the portal vessels. Although the hypothalamus is recognized to have autonomic activity and is capable of maintaining a tonic release of gonadotropin even when disconnected from the rest of the brain (Halász and Gorski 1967), a number of stimuli can affect its activity. The most clear evidence in this respect is provided by coitus in the so-called reflex ovulators. Many other internal as well as external stimuli of different modalities are known to exert a modulating influence on the endocrine function. These signals, of diverse origin, reach the hypothalamic neurons by different routes being the neural information transformed into a chemical one before influencing the anterior pituitary. The pool of hypothalamic neurons which secrete the releasing and inhibitory factors thus form the final common pathway for the pituitary gland.